Oil cooling often occurs with oil/air coolers, using thermostats that respond to corresponding oil temperatures. These solutions are certainly quite effective at smaller cooler sizes, but with greater cooling output and correspondingly larger coolers a situation results, in which unduly low oil temperatures occur in many operating states, which adversely effect fuel consumption and lifetime of the internal combustion engine.
For this reason, a switch has since been made to optimize the oil temperature, i.e., to cool or heat the oil, as required. For this purpose, an additional oil/water heat exchanger is integrated in the cooling loop, which is connected or disconnected as required by means of a thermostat that responds to oil temperature. These thermostats often must be activated with an electrical control. Although this group of solutions was to offer optimized oil temperature, it also entails significant costs on the equipment side.
Oil/water heat exchangers integrated in the normal water loop are also used for transmission fluid cooling, which are often incorporated in a water tank of the radiator, but also can be provided separately. Only cooling is achieved in this group of solutions, but not preheating or heating.
It is stated in DE-OS 41 04 093 that both rapid heating of the passenger compartment and rapid achievement of the operating temperature of the engine and transmission fluid are the problem in the starting phase of internal combustion engines. A virtual cooling management system has been proposed here to better deal with these partially contradictory constraints, in which a microprocessor is supposed to influence the output of the different heat exchangers, based on signals from a series of temperature sensors in the different loops. This installation appears to be quite expensive and has a complicated and therefore vulnerable technical structure.